I am using Ubuntu 9.04 Jaunty Jackalope and recently encountered a problem updating the package sources or when reloading the repositories so was unable to add new repos via synaptic or apt-get. The console output was something like
Get: http://ftp.debian.org sid/main Sources
Get: http://ftp.debian.org sid/contrib Sources
Get: http://ftp.debian.org sid/non-free Sources
I searched for solutions and found it here.
It involves uninstalling two packages namely ia32-archive and ia32-apt-get via synaptic or apt-get.